1. Field of the Invention
The present invention relates to a sheet post-processing apparatus for performing post-processing such as punching, stamping, bunch alignment, paper binding and paper folding on sheets carried out of an image forming apparatus such as a copier and printer, and an image forming apparatus using the sheet post-processing apparatus, and more specifically, to a sheet post-processing apparatus that is most suitable for being installed and used in space provided in the main body of the image forming apparatus.
2. Description of the Prior Art
Generally, with the progression of multifunction in the image forming apparatus, sheet post-processing apparatuses which perform post-processing on printed sheets are being developed. In such a sheet post-processing apparatus, for example, a sheet is subjected to first post-processing such as a punching and stamping using a punching apparatus and a stamping apparatus, the sheets are then made in bunch form, the bunches are displaced alternately in position and discharged in a bunch shift (JOG) mechanism, or the sheets in bunch form are bound using a stapler apparatus, or adhesive apply apparatus, the processed sheets are further subjected to paper folding such as two-folding and three-folding, the sheets are thus subjected to the second post-processing, and the processed sheet bunch selectively subjected to some post-processing is stored in a collection tray. Then, such a sheet post-processing apparatus, which is installed with each unit of a wide variety of post-processing apparatuses and upsized, is connected to the side of the image forming apparatus and used.
In recent years, for example, as disclosed in Patent Document 1 (Japanese Patent Application Publication No. 2006-248686), the sheet post-processing apparatus itself is configured in a compact size, is not connected to the side of the image forming apparatus, but is capable of being installed in space provided in the image forming apparatus, and such a sheet post-processing apparatus is becoming widespread.
The image forming apparatus is equipped with an apparatus body in the shape of a U provided with space in the center portion, and a compact sheet post-processing apparatus inside the space provided in the center portion. In addition, in contrast to the sheet post-processing apparatus connected to the side of the image forming apparatus, such a sheet post-processing apparatus which is installed in the image forming apparatus comprised of a U-shaped apparatus body is so-called the in-body finisher.
Further, as distinct from the above-mentioned sheet post-processing apparatus which is installed with a wide variety of post-processing apparatuses and is upsized, in the sheet post-processing apparatus as disclosed in Patent Document 1, post-processing units with a high frequency are selected corresponding to a use environment where the apparatus is installed, the selected post-processing units are connected, and the compact size is thereby attained. More specifically, in this case, the apparatus is comprised of a punch unit for punching holes in predetermined portions of a sheet carried out of the main-body apparatus when necessary, a staple unit which loads sheets passed through the punch unit in bunch form in an intermediate collection part and binds the loaded sheet bunch with staples, and a collection tray which stores and collects the sheet bunch which is subjected to binding processing in the staple unit and discharged. Meanwhile, the punch unit is attached to the post-processing apparatus frame side, and the staple unit is attached to the post-processing apparatus frame to be able to slide in the sheet carrying-out direction with respect to the fixed and supported punch unit. Further, the collection tray capable of moving up and down is attached to the stapler unit.
Further, as well as Patent Document 1, Japanese Patent Application Publication No. 2006-219224 is also known.
However, in the image forming apparatus as described in above-mentioned Patent Document 1, there is a case that a sheet remains in the sheet post-processing apparatus or in a transport path in front of the apparatus. Then, the removal operation of the remaining sheet varies with the remaining position of the remaining sheet. For example, when a sheet remains in the transport path in front of the sheet post-processing apparatus, the sheet is not removed only by pulling out the staple unit from the apparatus body, the punch unit, which is beforehand installed to be capable of being pulled out toward the front in the direction perpendicular to the sheet transport direction, is pulled out, a lower guide plate of a pair of upper and lower guide plates constituting the transport path is opened downward with space between the punch unit and the transport path opened, and the sheet remaining in the path is removed. Meanwhile, when a sheet remains in a transport path of the sheet post-processing apparatus, a joint between the staple unit and the apparatus body is released, the staple unit is slid and pulled out, clearance is thereby created between the staple unit and the punch unit, and it is possible to remove the remaining sheet from the clearance.
In an image forming apparatus provided with such a sheet post-processing apparatus, there are two technical problems as described below.
First, as the first problem, in the structure in which only the staple unit is supported slidably with respect to the apparatus body and pulled out with the punch unit left on the apparatus body side, in removing a sheet left in front of the above-mentioned sheet post-processing apparatus, the structure needs to enable the punch unit to be pulled out to the front side with respect to the apparatus body, and a slide mechanism specific to the punch unit is required. Such a mechanism does not only impair the compact feature, but also leads to a tendency to tilt up and down by pulling out in the direction perpendicular to the sheet carrying-out direction, a sheet guide surface of the punch unit is inclined with respect to the sheet carrying-out guide plane by the tilt, the sheet passage distance is narrowed on either the front side or the back side by the inclination, and as a result, such a narrowed portion causes a carrying-out sheet to be caught therein and becomes the factor of the remaining.
Further, as the second problem, when the punch unit is pulled out toward the front side in the direction perpendicular to the sheet carrying-out direction and the above-mentioned remaining sheet is removed, the transport path in which the remaining sheet is present hides at the back of the punch unit that is pulled out to the front side, the operator peeps through an opening opened by pulling out the staple unit, and needs to pull the remaining sheet out of the transport path hiding at the back of the opening to remove, and the work is not only difficult to perform but also lacks safety because the operator inserts his/her hand while folding in removing the remaining sheet and the hand comes into contact with other parts.